Protection type display device

ABSTRACT

A projection-type display device includes a shielding unit and image signal correction units that divide the picture plane of the spatial light modulation element into a plurality of areas and perform correction on the image signal applied to the spatial light modulation element according to the current shielding amount of the shielding unit for each of the plurality of areas. Accordingly, appropriate uniformity correction is performed even when there is a change in the angular distribution of light emitted from the spatial light modulation element and reaching the screen.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/523,515, filed Aug. 15, 2005, which is a national stage applicationunder 35 U.S.C. §371 of International Publication No. PCT/JP04/08389,filed Jun. 9, 2004, which claims priority of Japanese Patent ApplicationNo. 2003-169788, filed on Jun. 13, 2003, the disclosures of which arehereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Technical Field

This invention relates to a projection-type display device (projector),and in particular to a projection-type display device havingdiaphragm-like shielding means to improve contrast.

2. Background Art

There has been widespread adoption of projection-type display devices,in which, in conformance to an electrical signal applied to a spatiallight modulation element, light incident on the spatial light modulationelement is spatially modulated and emitted, and the emitted light iscondensed and projected to display an image. Such a projection-typedisplay device conventionally has a lamp and condensing mirror as alight source, and also has an illumination optical system in which lightemitted from the light source is condensed and made incident on thespatial light modulation element; and light from the spatial lightmodulation element is projected onto a screen or similar by a projectionlens.

At present, representative spatial light modulation elements are thosehaving internally a liquid crystal material, which by applying anelectric field to the liquid crystals cause rotation of the oscillationdirection of the incident polarized light (hereafter called the “liquidcrystal type”), and those which have minute moveable mirrors for eachpixel, and in which incident light is reflected by the minute moveablemirrors, with spatial modulation performed by changing the retentionangles of the minute moveable mirrors according to the image signal(hereafter called the “DMD® (digital micromirror device) type”).

FIG. 1 shows the basic configuration of a liquid crystal-typeprojection-type display device (liquid crystal projector). Light isemitted from a light source 21 toward a reflecting mirror 22. Much ofthe light is condensed at a liquid crystal element (liquid crystalpanel) 25 which is the spatial light modulation element by thereflecting mirror 22 and an illumination optical system 23. Thecondensed light is made incident on a polarizer 24 before being incidenton the liquid crystal element 25, to extract light polarized in onedirection. Then, an image signal is applied to the liquid crystalelement 25, so that the light emitted from the polarizer 24 and incidenton the liquid crystal element 25 is spatially modulated, with thepolarization direction rotated according to the image signal. Lightleaving the liquid crystal element 25 is incident on an analyzer 26, andthe light for projection is selected. Light emitted from the analyzer 26is incident on a projection lens 27, and is projected to display animage on the screen (not shown).

Next, FIG. 2 shows the basic configuration of a DMD®-typeprojection-type display device (DMD® projector). Light is emitted from alight source 31 toward a reflecting mirror 32. Much of the light iscondensed at the DMD® element (DMD® panel) 34, which is the spatiallight modulation element, by the reflecting mirror 32 and anillumination optical system 33. An image signal is applied to the DMD®element 34, the incident light is spatially modulated, the inclinationsof the minute movable mirrors are changed according to the image signal,and the emission direction of light is changed. Light selected by theDMD® element 34 is incident on a projection lens 35, and is projectedonto a screen (not shown) to display an image.

However, in comparisons of the images displayed by projection-typedisplay devices with those of other image display devices, the lowcontrast of images displayed by projection-type display devices isnoted. Here “contrast” means the brightness ratio when a white screen isdisplayed and when a black screen is displayed.

As shown in FIGS. 1 and 2, even if a projection-type display device isused to display a black screen, a portion of the light, albeit a smallamount, is incident on the projection lens. This is because the lightsource is always being operated.

As a measure to resolve the above inconvenience, in recent yearsdiaphragms have been provided in the illumination optical system or atthe projection lens in projection-type display devices (refer to forexample Japanese Published Patent Application No. 2001-264728(paragraphs 0049 to 0054 and FIG. 1)).

The improvement in contrast when an aperture is provided is due to thefollowing reason. In the case of a liquid crystal projector, acharacteristic of liquid crystal elements is that the larger the angleof incidence on the liquid crystal panel surface, the greater thedegradation in contrast. Consequently in the liquid crystal projectorshown in FIG. 1, by providing a diaphragm 41 within the illuminationoptical system 23 or in proximity to the illumination optical system 23as shown in FIG. 3, the angle of rays incident on the liquid crystalelement 25 can be decreased, so that contrast is improved.

Alternatively, by providing a diaphragm 41 within the projection lens 27in the liquid crystal projector of FIG. 1, as shown in FIG. 4, so thatthose rays emitted from the liquid crystal element 25 that are incidenton the liquid crystal panel at large angles are blocked by the diaphragm41, and contrast is improved.

In the case of a DMD® projector, on the other hand, as explained above,when a black screen is displayed the light incident on the DMD® elementis caused not to be incident on the projection lens. However, because aDMD® element is an aggregation of minute mirrors, light scatteringoccurs among the mirrors. Accordingly, there exists some light whichordinarily should not be directed toward the projection lens but is infact incident on the projection lens. In order to prevent this lightfrom actually being projected insofar as possible, a diaphragm may beprovided in the projection lens, so that contrast can be improved.

As explained above, there have been conventional projection-type displaydevices in which contrast has been improved by installing a diaphragm.However, there is also the inconvenience that use of a diaphragm whichblocks a fixed amount of light (for example, an aperture diaphragm withfixed aperture shape) results in a decrease in brightness whendisplaying a white screen.

As a method for avoiding this inconvenience, a variable diaphragm(diaphragm capable of varying the amount of light to be blocked) may beused, enabling a plurality of states when opening the diaphragm and whenblocking light. The problem with contrast in a projected image is due tothe brightness of the projection environment. In a bright room, the roombrightness (room illumination, sunlight and similar) causes light to beincident on the screen regardless of whether a projection-type displaydevice is present. Hence even if a black screen is displayed, because ofoutside light, fading of black portions due to the device does notbecome a problem. White screen brightness exceeds the outside light isnecessary.

Conversely, in the case where there is no outside light, fading of ablack screen becomes prominent. On the other hand, because the area isdark, brightness in a white screen is not as necessary. This is becausehuman eyes adjust to the brightness.

Hence in an environment in which there is outside light, the diaphragmis opened, white colors are made brighter, and a high-brightness imageis presented. On the other hand, in an environment with no outsidelight, the diaphragm is closed, white is suppressed, and contrast isincreased. In this way, by using a variable diaphragm, a balance betweenbrightness and contrast can be achieved.

However, when a variable diaphragm is opened and closed in this way, theangular distribution of light emitted from the spatial light modulationelement and arriving at the screen is different when the diaphragm isopened and when it is closed. This is because, as explained above, aportion of the light incident on the spatial light modulation elementand a portion of the light emitted from the spatial light modulator isblocked and prevented from reaching the screen. This is the means ofincreasing the contrast, but as a consequence the following problems mayarise.

In a liquid crystal element, the thickness of the portion into whichliquid crystals are sealed (the liquid crystal layer) may not beuniform. Even if a voltage at the same level were applied to all thepixels in a liquid crystal panel, because the thickness of the liquidcrystal layer differs in different areas, the incident light may not beoptically modulated to the same extent. In other words, in the sameliquid crystal panel, the graph relating the applied voltage (V) to thetransmittance (T) (the VT curve) may not be the same depending on thearea of the effective picture plane.

In this state, appropriate light modulation is not possible depending onthe location in the picture plane, so that differences arise between theapplied image signal and the projected image. For example, even in acase in which an image signal is input at a level corresponding to atransmittance of 50%, the transmittance is not 50% for all locations ofthe picture plane, so that brightness is uneven in the projected image.

In order to alleviate this brightness unevenness, this applicant hasdisclosed technology, in Japanese Published Patent Application No.H11-113019, to divide the picture plane of a liquid crystal panel into aplurality of areas, and to perform correction on the image signalapplied to the liquid crystal panel according to the VT curvecharacteristics and similar with respect to each of these areas(hereafter called “uniformity correction technology”).

However, even at the same location in the picture plane, the VT curvechanges with the angular distribution of light incident on the liquidcrystal panel. Consequently if there are changes, due to opening andclosing of the variable diaphragm, in the angular distribution of lightreaching the screen after emission from the liquid crystal panel (ifopening and closing of a variable diaphragm on the illumination opticalsystem side cause changes in the angular distribution of light incidenton the liquid crystal panel, or opening and closing of a variablediaphragm on the projection lens side cause changes in the angulardistribution of light projected from the projection lens at the time ofincidence on the liquid crystal panel), then even when using suchuniformity correction technology, appropriate correction cannot beperformed, and brightness unevenness occurs in the projected image.

In the above, cases have been explained in which by opening and closinga variable diaphragm, the angular distribution of light emitted from aliquid crystal panel and reaching a screen changes; however, in additionto the above, reasons for a change in the angular distribution of lightemitted from a liquid crystal panel and reaching a screen may includecases in which the zoom position of a projection lens comprising a zoomlens, with variable focal length, is changed, and cases in which theliquid crystal projector has a projection lens which can be replaced,and the projection lens is replaced with a lens having a different fnumber.

In light of the above, an object of this invention is to provide aprojection-type display device which can perform appropriate uniformitycorrection even in cases when the angular distribution of light emittedfrom the spatial light modulation element and reaching the screenchanges.

SUMMARY OF THE INVENTION

In order to achieve this object, the applicant proposes aprojection-type display device, including a light source; a spatiallight modulation element which modulates incident light according to anapplied image signal and emits the modulated light; an illuminationoptical system which condenses light from the light source andilluminates the spatial light modulation element; a projection lenswhich projects light emitted from the spatial light modulation element;shielding means, positioned along the path of light on the side ofeither the illumination optical system or the projection lens withrespect to the spatial light modulation element, and which varies theamount of shielding of transmitted light; and image signal correctionmeans which divides the picture plane of the spatial light modulationelement into a plurality of areas, and performs correction on the imagesignal applied to the spatial light modulation element according to thecurrent shielding amount of the shielding means for each of theplurality of areas.

In this projection-type display device (a first projection-type displaydevice of this invention), the shielding amount of the shielding meansis reduced in an environment with outside light, so that white is madebright and a high-brightness image can be presented, and the shieldingamount of the shielding means is increased in an environment with nooutside light, so that white is suppressed and contrast can be improved,and consequently a balance can be achieved between brightness andcontrast.

Further, this projection-type display device includes image signalcorrection means to perform correction on the image signal applied tothe spatial light modulation element, according to the current shieldingamount of the shielding means, for each of the plurality of areas intowhich the picture plane of the spatial light modulation element isdivided. Hence different correction is performed according to changes inthe shielding amount of the shielding means, even for image signals atthe same location of the picture plane of the spatial light modulationelement.

In this way, correction of the image signal is performed which differsdepending on changes in the shielding amount of the shielding means,even for an image signal at the same location of the picture plane ofthe spatial light modulation element; hence even if there is a change inthe angular distribution of light emitted from the spatial lightmodulation element and reaching the screen due to changes in theshielding amount of the shielding means, appropriate uniformitycorrection can be performed.

In one example, it is preferable that in this projection-type displaydevice the image signal correction means perform correction, for eacharea, according to the characteristic of the light output level for anarea with respect to the level of application of the image signal and tothe current shielding amount of the shielding means.

By this means, even in the case where the characteristic of the spatiallight modulation element is different depending on the area and moreovervaries according to the angular distribution of light incident on thespatial light modulation element changes, appropriate uniformitycorrection can be performed.

In one example, it is preferable that this projection-type displaydevice further includes storage means to store a plurality of correctiondata sets according to the shielding amount of the shielding means, andthat the image signal correction means perform correction according tothe current shielding amount of the shielding means, referring tocorrection data from the storage means.

As a result, appropriate uniformity correction according to changes inthe shielding amount of the shielding means can be performed even morequickly than in cases in which correction data is obtained bycomputation according to the current shielding amount of the shieldingmeans.

Next, the applicant of the present invention proposes a projection-typedisplay device including a light source; a spatial light modulationelement which modulates incident light according to an applied imagesignal, and emits the modulated light; an illumination optical systemwhich condenses light from the light source and illuminates the spatiallight modulation element; a projection lens including a zoom lens whichprojects the light emitted from the spatial light modulation element;and image signal correction means which divides the picture plane of thespatial light modulation element into a plurality of areas, and performscorrection on the image signal applied to the spatial light modulationelement, for each of the divided areas, according to the f number at thecurrent zoom position of the projection lens.

This projection-type display device (a second projection-type displaydevice of this invention) includes image signal correction means whichperforms correction on the image signal applied to the spatial lightmodulation element, for each of the plurality of areas into which thepicture plane of the spatial light modulation element is divided,according to the f number at the current zoom position of the projectionlens including a zoom lens. Hence different correction of the imagesignal at the same location in the picture plane of the spatial lightmodulation element is performed, according to the zoom position of theprojection lens.

In this way, different correction of the image signal is performed evenat the same location in the picture plane of the spatial lightmodulation element, depending on the zoom position of the projectionlens, so that appropriate uniformity correction can be performed even inthe case where there are changes in the angular distribution of lightemitted from the spatial light modulation element and reaching thescreen due to changes in the projection lens zoom position.

In one example, it is preferable that in this projection-type displaydevice the image signal correction means perform correction, for eachdivided area, according to the characteristic of the light output levelin the area with respect to the image signal application level, andaccording to the f number at the current zoom position of the projectionlens.

By this means, even in the case where the characteristics of the spatiallight modulation element differ for different areas and also changedepending on the angular distribution of light incident on the spatiallight modulation element, appropriate uniformity correction can beperformed.

In one example, it is preferable that this projection-type displaydevice further include storage means to store a plurality of correctiondata sets according to the f number of the projection lens, and that theimage signal correction means perform correction according to f numberat the current zoom position of the projection lens, referring tocorrection data from the storage means.

As a result, appropriate uniformity correction according to changes inthe zoom position of the projection lens can be performed more quicklythan by computation of correction data according to the f number at thecurrent zoom position of the projection lens.

Further, in one example, it is preferable that this projection-typedisplay device further include judgment means to judge the current zoomposition of the projection lens, so that the image signal correctionmeans performs correction according to the f number at the current zoomposition of the projection lens, based on the judgment result of thejudgment means.

As a result, appropriate uniformity correction can be performedautomatically according to changes in the zoom position of theprojection lens.

Next, the applicant of the present invention proposes a projection-typedisplay device including: a light source; a spatial light modulationelement which modulates incident light according to an applied imagesignal, and emits the modulated light; and an illumination opticalsystem which condenses light from the light source and illuminates thespatial light modulation element; in which a projection lens whichprojects light emitted from the spatial light modulation element can bereplaced with a plurality of different types of projection lenses withdifferent f numbers; and further including image signal correction meanswhich divides the picture plane of the spatial light modulation elementinto a plurality of areas, and performs correction on the image signalapplied to the spatial light modulation element, for each of theseareas, according to the f number of the currently mounted projectionlens.

This projection-type display device (a third projection-type displaydevice of this invention) includes image signal correction means whichperforms correction on the image signal applied to the spatial lightmodulation element, for each area of the plurality of areas into whichthe picture plane of the spatial light modulation element is divided,according to the f number of the projection lens currently mounted amonga plurality of projection lenses with different f numbers. Hence animage signal at the same location in the picture plane of the spatiallight modulation element is corrected differently according to the fnumber of the mounted projection lens.

In this way, correction is performed differently, depending on the fnumber of the currently mounted projection lens, even for image signalsat the same location of the spatial light modulation element, so thatappropriate uniformity correction can be performed even if there is achange in the angular distribution of light emitted from the spatiallight modulation element and reaching the screen due to replacement ofthe projection lens with a projection lens having a different f number.

Further in one example, it is preferable that in this projection-typedisplay device the image signal correction means performs correction,for each area, according to the characteristic of the light output levelfor the area with respect to the image signal application level, and tothe f number of the currently mounted projection lens.

By this means, even in the case where the characteristics of the spatiallight modulation element are different for different areas, and alsochange due to the angular distribution of light incident on the spatiallight modulation element, appropriate uniformity correction can beperformed.

In one example, it is preferable that this projection-type displaydevice further include storage means which stores a plurality ofcorrection data sets according to the f numbers of a plurality of typesof projection lens, and that the image signal correction means performscorrection referring to the correction data from the storage means,according to the f number of the currently mounted projection lens.

As a result, appropriate uniformity correction according to theprojection lens replacement can be performed more quickly than bycomputation of correction data according to the f number of thecurrently mounted projection lens.

Further in one example, it is preferable that this projection-typedisplay device further include judgment means to judge the f number ofthe currently mounted projection lens, and that the image signalcorrection means perform correction according to the f number of thecurrently mounted projection lens, based on the judgment result of thejudgment means.

By this means, appropriate uniformity correction can be performedautomatically according to replacement of the projection lens.

In one example, it is preferable that in this projection-type displaydevice, the image signal correction means perform correction referringto correction data from individual correction data storage means,possessed by the currently mounted projection lens, which storescorrection data to perform individual correction corresponding to theprojection lens.

Also preferred is a projection-type display device further includingstandard correction data storage means which stores correction dataaccording to the f number of a projection lens serving as a standard,and wherein the image signal correction means references standardcorrection data from this standard correction data storage means, anddifferential data is referenced to perform correction from theindividual correction data storage means, possessed by the currentlymounted projection lens, which stores differential data with respect tothis standard correction data in order to perform individual correctioncorresponding to the projection lens.

As a result, appropriate uniformity correction can be performedaccording to projection lens replacement, without requiring the storageof numerous correction data sets in the projection-type display devicemain unit, even in the cases where there are numerous types ofreplaceable projection lenses.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the basic configuration of a liquid crystal projector;

FIG. 2 shows the basic configuration of a DMD® projector;

FIG. 3 shows a conventional liquid crystal projector provided with adiaphragm;

FIG. 4 shows a conventional liquid crystal projector provided with adiaphragm;

FIG. 5 shows an example of the configuration of a liquid crystalprojector to which this invention is applied;

FIG. 6 is a block diagram showing an example of the configuration of thethree-dimensional correction unit of FIG. 5;

FIG. 7 shows an example of the configuration of another liquid crystalprojector to which this invention is applied;

FIG. 8 shows a change in the zoom position of the liquid crystalprojector of FIG. 7;

FIG. 9 shows an example of the configuration of another liquid crystalprojector to which this invention is applied; and

FIG. 10 shows a modified example of the liquid crystal projector of FIG.9.

DETAILED DESCRIPTION Best Mode Of Carrying Out The Invention

Hereinafter, this invention is explained in detail using the drawings.FIG. 5 shows an example of the configuration of a liquid crystalprojector to which this invention is applied; units common to FIG. 1 areassigned the same symbols. Light is emitted from the light source 21toward the reflecting mirror 22. Much of the light is collected at theliquid crystal element (liquid crystal panel) 25, which is the spatiallight modulation element, by the reflecting mirror 22 and illuminationoptical system 23.

A variable diaphragm 1 is positioned in the vicinity of the illuminationoptical system 23. The variable diaphragm 1 is a mechanical shutter inwhich the area of the aperture portion can be changed; the area of thisaperture portion is increased and decreased by a variable-diaphragmdriving unit 2 (a motor which displaces the operating unit of thevariable diaphragm 1, and a motor driver or similar which drives themotor).

Light collected by the reflecting mirror 22 and illumination opticalsystem 23 passes through this variable diaphragm 1 and is incident onthe polarizer 24, to extract light polarized in one direction, beforebeing incident on the liquid crystal element 25. An image signal isapplied to the liquid crystal element 25, and light emitted from thepolarizer 24 and which is incident on the liquid crystal element 25 isspatially modulated, with the polarization direction rotated accordingto the image signal. Light leaving the liquid crystal element 25 isincident on the analyzer 26, and light to be projected is selected.Light emitted from the analyzer 26 is incident on the projection lens27, and is projected onto a screen (not shown) or similar to display animage.

An operation panel on the main unit and a remote controller of thisliquid crystal projector are not shown in the drawings, but a diaphragmadjustment button is provided to perform opening and closing operationof the variable diaphragm 1 (performing adjustment to make the area ofthe aperture portion large or small, in two stages). A CPU 6 controlseach unit within the liquid crystal projector; in the case where anoperation is performed using the diaphragm adjustment button to open thevariable diaphragm 1, the variable-diaphragm driving unit 2 iscontrolled to widen the variable diaphragm 1 (maximize the area of theaperture portion), and on the other hand in the case where an operationis performed to close the variable diaphragm 1 using the diaphragmadjustment button, the variable-diaphragm driving unit 2 is controlledto narrow the variable diaphragm 1 (reduce the area of the apertureportion compared with the maximum area).

The image signal applied to the liquid crystal element 25 is correctedby a white balance adjustment unit 3 and a gamma correction unit 4. Thewhite balance adjustment unit 3 adjusts the color temperature of theimage signal, and though omitted from the drawings, includes a gaincircuit to adjust the color temperature on the white side of the imagesignal, and a bias circuit to adjust the color temperature on the blackside of the image signal. The gamma correction unit 4 performs gammacorrection on the image signal from the white balance adjustment unit 3to adjust the image quality; though omitted from the drawings, a lookuptable is provided which stores characteristic curve data which is theopposite of the VT curve characteristics of conventional liquid crystalelements.

The three-dimensional correction unit 5 supplies, to the white balanceadjustment unit 3 and gamma correction unit 4, three-dimensionalinterpolation data C (X, Y, Z) for the level Z image signal at anarbitrary pixel G (X, Y) of the liquid crystal element 25, and as shownin FIG. 6, includes a horizontal/vertical synchronization counter 11,position block identification processor 12, coordinate data storage unit13, position computation processor 14, three-dimensional interpolationprocessor 15, and correction data storage unit 16.

The horizontal/vertical synchronization counter 11 is a counter whichidentifies the plane coordinates (X, Y) of a pixel when a pixel (signal)for correction processing is seen as a position in the display screen,that is, when the display screen is seen as a plane; the horizontalposition coordinate X output from this horizontal/verticalsynchronization counter 11 is zero-reset in sync with the horizontalsynchronization signal Hsync, and is incremented at each clock signalCLK, to serve as coordinate data representing the horizontal-directionposition of a pixel. The vertical position coordinate Y output from thehorizontal/vertical synchronization counter 11 is zero-reset in syncwith the vertical synchronization signal Vsync, and is incremented ateach horizontal synchronization signal Hsync, to serve as coordinatedata representing the vertical-direction pixel position. The clocksignal CLK is synchronized with changes on the time axis, and isconventionally referred to as a dot clock.

The coordinate data storage unit 13 is provided with a register to storecorrection center coordinate data (coordinate data for the center pointfor correction in the picture plane of the liquid crystal element 25)Xc, Yc; correction range coordinate data (coordinate data for thevertices of the range over which correction is necessary in the pictureplane of the liquid crystal element 25) X1, X2, Y1, Y2; and data Z1, Z2for the range of image signal levels over which correction will extend.At the time of factory adjustment or similar occasion, this registerstores correction center coordinate data and correction range coordinatedata, input in advance from an external device.

The coordinates X, Y of the pixel G(X, Y) are supplied by thehorizontal/vertical synchronization counter 11 to the position blockidentification processor 12, and data stored in the coordinate datastorage unit 13 is supplied; and the range over which correction isnecessary is further divided into a plurality of position blocks.

The position computation processor 14 judges at which address and inwhich position block a pixel G(X, Y) is positioned from the coordinatesX, Y of the pixel G(X, Y) supplied from the horizontal/verticalsynchronization counter 11, the data stored in the coordinate datastorage unit 13, and from the suffix n identifying the position blocksupplied by the position block identification processor 12, and outputsthe judgment result as the address data Xb, Yb. The correction datastorage unit 16 is provided with a register to store correction data Cc(Xc, Yc, Zc) at the correction center coordinate Gc, and similar.

The three-dimensional interpolation processor 15 interpolates the outputlevels for level Z applied image signals at arbitrary coordinates G(X,Y), based on address data Xb, Yb from the position computation processor14 and the correction data Cc stored in the correction data storage unit16, to create three-dimensional interpolation data C(X, Y, Z). Thisthree-dimensional interpolation data C(X, Y, Z) is supplied to the whitebalance adjustment unit 3 and gamma correction unit 4.

The detailed configuration and operation of those white balanceadjustment unit 3, gamma correction unit 4, and three-dimensionalcorrection unit 5 are described in Japanese Published Patent ApplicationNo. 11-113019, filed by this applicant; by means of these units, thepicture plane of the liquid crystal element 25 is divided into aplurality of areas, and uniformity correction (white balance adjustmentand gamma correction) can be applied to the image signal applied to theliquid crystal element 25, according to the VT curve characteristic foreach area and to the level of the image signal.

However, as shown in FIG. 6, two registers storing correction data Ccare provided in the correction data storage unit 16 of thethree-dimensional correction unit 5: a register 17 to store correctiondata Cc used when the variable diaphragm 1 is opened, and a register 18to store correction data Cc used when the variable diaphragm 1 isclosed.

At the time when adjusting the liquid crystal projector at the factory,color unevenness and brightness unevenness in the projected image whenthe variable diaphragm 1 is open, and color unevenness and brightnessunevenness in the projected image when the variable diaphragm 1 isclosed, are measured respectively; correction data Cc (according to theVT curve characteristics for each area of the picture plane of theliquid crystal element 25, corresponding to the angular distribution oflight incident on the liquid crystal element 25 with the variablediaphragm 1 in the open state), to compensate for color unevenness andbrightness unevenness when the variable diaphragm 1 is open, is storedin the register 17; and correction data Cc (according to the VT curvecharacteristics for each area of the picture plane of the liquid crystalelement 25, corresponding to the angular distribution of light incidenton the liquid crystal element 25 with the variable diaphragm 1 in theclosed state), to compensate for color unevenness and brightnessunevenness when the variable diaphragm 1 is closed, is stored in theregister 18.

In the case where operation is performed to open the variable aperture 1using the above-described diaphragm adjustment button, the CPU 6controls the three-dimensional correction unit 5 and causes thethree-dimensional interpolation processor 15 to refer to theinterpolation data Cc in the register 17 among the registers 17, 18 inthe correction data storage unit 16; on the other hand, in the casewhere operation is performed to close the variable aperture 1 using theabove-described diaphragm adjustment button, the CPU 6 controls thethree-dimensional correction unit 5 and causes the three-dimensionalinterpolation processor 15 to refer to the interpolation data Cc in theregister 18 among the registers 17, 18 in the correction data storageunit 16.

Next, operation of the liquid crystal projector is explained.

When using the liquid crystal projector in an environment with outsidelight, the user employs the above-described diaphragm adjustment buttonto perform an operation to open the variable diaphragm 1. Under controlby the CPU 6, the area of the aperture portion of the variable diaphragm1 is maximized, so that the shielding amount by the variable diaphragm 1is reduced, white is made brighter, and a high-brightness image can bedisplayed.

On the other hand, when using the liquid crystal projector in anenvironment with no outside light, the user employs the above-describeddiaphragm adjustment button to perform an operation to close thevariable diaphragm 1. Under control by the CPU 6, the area of theaperture portion of the variable diaphragm 1 is reduced, so that theshielding amount by the variable diaphragm 1 is increased, white issuppressed, and contrast is increased. By this means, a balance betweenbrightness and contrast is achieved.

When the variable diaphragm 1 is opened, three-dimensional interpolationdata C(X, Y, Z), obtained under control of the CPU 6 based on correctiondata Cc (correction data to compensate for color unevenness andbrightness unevenness in a projected image when the variable diaphragm 1is open) in the register 17 of the correction data storage unit 16, issupplied to the white balance adjustment unit 3 and gamma correctionunit 4 from the three-dimensional correction unit 5. By this means,uniformity correction (white balance adjustment and gamma correction)are performed on the image signal applied to the liquid crystal element25 in the white balance adjustment unit 3 and gamma correction unit 4,to compensate for color unevenness and brightness unevenness in theprojected image when the variable diaphragm 1 is open.

On the other hand, when the variable diaphragm 1 is closed,three-dimensional interpolation data C(X, Y, Z), obtained under controlof the CPU 6 based on correction data Cc (correction data to compensatefor color unevenness and brightness unevenness in a projected image whenthe variable diaphragm 1 is closed) in the register 18 of the correctiondata storage unit 16, is supplied to the white balance adjustment unit 3and gamma correction unit 4 from the three-dimensional correction unit5. By this means, uniformity correction (white balance adjustment andgamma correction) are performed on the image signal applied to theliquid crystal element 25 in the white balance adjustment unit 3 andgamma correction unit 4, to compensate for color unevenness andbrightness unevenness in the projected image when the variable diaphragm1 is closed.

By thus performing correction on the image signal which differs,according to whether the variable diaphragm 1 is open or closed, evenfor the same level at the same location in the picture plane of theliquid crystal element 25 in the liquid crystal projector, appropriateuniformity correction can be performed even when there is a change inthe angular distribution of light emitted from the liquid crystalelement 25 and reaching the screen, according to the open or closedstate of the variable diaphragm 1.

Further, registers 17 and 18, storing two sets of correction data Cceach corresponding to characteristic of each area of the picture planeof the liquid crystal element 25 according to whether the variablediaphragm 1 is open or closed, are provided in the correction datastorage unit 16 of the three-dimensional correction unit 5, so thatappropriate uniformity correction according to the open or closed stateof the variable diaphragm 1 can be performed more quickly than in thecase where correction data Cc is computed according to the current openor closed state of the variable diaphragm 1.

Next, FIG. 7 shows an example of the configuration of another liquidcrystal projector to which this invention is applied; units common toFIGS. 1, 5 and 6 are assigned the same symbols. This liquid crystalprojector is not provided with a variable diaphragm, but has aprojection lens 28 including zoom lenses with f numbers from 1.85 to2.2.

Though not shown in the drawings, the operation panel or remotecontroller of this liquid crystal projector is provided with a zoomadjustment button to perform operations to adjust the zoom position ofthe projection lens 28. Based on operation of this zoom adjustmentbutton, the CPU 6 controls the zoom position of the projection lens 28.

In FIG. 7, a state in which the zoom position of the projection lens 28is on the broad-angle side (a state in which the f number is 1.85) isshown. FIG. 8 shows a state in which the zoom position of the projectionlens 28 is on the telephoto side (a state in which the f number is 2.2)(in FIG. 8, the white balance adjustment unit 3, gamma correction unit4, three-dimensional correction unit 5, and CPU 6 are omitted) As isshown in those drawings also, the angular distribution of light emittedfrom the liquid crystal element 25 and reaching the screen changesaccording to changes in the zoom position of the projection lens 28.

When this liquid crystal projector is adjusted at the factory, colorunevenness and brightness unevenness in the projected image in the statein which the zoom position of the projection lens 28 is on thebroad-angle side (the state of FIG. 7), and color unevenness andbrightness unevenness in the projected image in the state in which thezoom position of the projection lens 28 is on the telephoto side (thestate of FIG. 8), are each measured; correction data Cc to compensatefor color unevenness and brightness unevenness when the zoom position ofthe projection lens 28 is on the broad-angle side (according to the VTcurve characteristics in each area of the picture plane of the liquidcrystal element 25, corresponding to the incident angle distributionwhen light to be projected from the projection lens 28 is incident onthe liquid crystal element 25 in the state in which the zoom position ofthe projection lens 28 is on the broad-angle side) is stored in theregister 17 (FIG. 6) of the correction data storage unit 16 of thethree-dimensional correction unit 5; and correction data Cc tocompensate for color unevenness and brightness unevenness when the zoomposition of the projection lens 28 is on the telephoto side (accordingto the VT curve characteristics in each area of the picture plane of theliquid crystal element 25, corresponding to the incident angledistribution when light to be projected from the projection lens 28 isincident on the liquid crystal element 25 in the state in which the zoomposition of the projection lens 28 is on the telephoto side) is storedin the register 18.

When operation is performed using the above-described zoom adjustmentbutton to move the zoom position of the projection lens 28 to thebroad-angle side, the CPU 6 controls the three-dimensional correctionunit 5 to cause the three-dimensional interpolation processor 15 torefer to the correction data Cc in register 17 among the registers 17and 18 of the correction data storage unit 16; on the other hand, whenoperation is performed using the above-described zoom adjustment buttonto move the zoom position of the projection lens 28 to the telephotoside, the CPU 6 controls the three-dimensional correction unit 5 tocause the three-dimensional interpolation processor 15 to refer to thecorrection data Cc in register 18 among the registers 17 and 18 of thecorrection data storage unit 16.

Other than the above, the configuration of this liquid crystal projectoris the same as the liquid crystal projector of FIG. 5.

Next, operation of this liquid crystal projector is explained.

When a user operates the above-described zoom adjustment button, thezoom position of the projection lens 28 is adjusted, under the controlof the CPU 6.

When the zoom position of the projection lens 28 is adjusted to thebroad-angle side, under the control of the CPU 6, three-dimensionalinterpolation data C(X, Y, Z) obtained based on the correction data Cc(correction data to compensate for color unevenness and brightnessunevenness in the state in which the zoom position of the projectionlens 28 is on the broad-angle side) in the register 17 of the correctiondata storage unit 16 is supplied to the white balance adjustment unit 3and gamma correction unit 4 from the three-dimensional correction unit5, with. By this means, uniformity correction (white balance adjustmentand gamma correction) of the image signal applied to the liquid crystalelement 25 are performed in the white balance adjustment unit 3 andgamma correction unit 4 so as to compensate for color unevenness andbrightness unevenness in the state in which the zoom position of theprojection lens 28 is on the broad-angle side.

On the other hand, when the zoom position of the projection lens 28 isadjusted to the telephoto side, under the control of the CPU 6,three-dimensional interpolation data C(X, Y, Z) obtained based on thecorrection data Cc (correction data to compensate for color unevennessand brightness unevenness in the state in which the zoom position of theprojection lens 28 is on the telephoto side) in the register 18 of thecorrection data storage unit 16 is supplied to the white balanceadjustment unit 3 and gamma correction unit 4 from the three-dimensionalcorrection unit 5. By this means, uniformity correction (white balanceadjustment and gamma correction) of the image signal applied to theliquid crystal element 25 are performed in the white balance adjustmentunit 3 and gamma correction unit 4 so as to compensate for colorunevenness and brightness unevenness in the state in which the zoomposition of the projection lens 28 is on the telephoto side.

Thus by performing different correction on the image signal even at thesame level in the same location of the picture plane of the liquidcrystal element 25, according to the zoom position of the projectionlens 28, appropriate uniformity correction can be performed even whenthere is a change, due to the zoom position of the projection lens 28,in the angular distribution of light emitted from the liquid crystalelement 25 and reaching the screen.

Further, registers 17 and 18 are provided in the data storage unit 16 ofthe three-dimensional correction unit 5 to store two sets of correctiondata Cc corresponding to the characteristic of each area in the pictureplane of the liquid crystal element 25, according to the zoom positionof the projection lens 28; hence appropriate uniformity correction canbe performed, according to the zoom position of the projection lens 28,more quickly than when computing the correction data Cc according to thezoom position of the projection lens 28.

Further, the CPU 6 can judge the current zoom position of the projectionlens 28 and perform correction according to the f number at the currentzoom position of the projection lens 28 based on the judgment result, sothat appropriate uniformity correction can be performed automaticallyaccording to changes in the zoom position of the projection lens 28.

Next, FIG. 9 shows an example of the configuration of another liquidcrystal projector to which this invention is applied; units common toFIGS. 1, 5 and 6 are assigned the same symbols. This liquid crystalprojector is not provided with a variable diaphragm, but as theprojection lens, two projection lenses, with f numbers of 1.85 and of2.2, can be used replaceably. The angular distribution of light emittedfrom the liquid crystal element 25 and reaching the screen changesaccording to the f number of the mounted projection lens.

As a projection lens mounted in this liquid crystal projector, a lensprovided with an f number notification unit 29 a, shown as theprojection lens 29 in the drawing, is used. The f number notificationunit 29 a notifies the CPU 6 of the liquid crystal projector of its ownf number (1.85 or 2.2); and by mounting the projection lens 29 on theliquid crystal projector, data indicating the f number is stored inmemory (for example ROM) connected to the CPU 6. By reading data fromthis memory, the CPU 6 determines the f number of the mounted projectionlens. (In another example, the f number notification unit 29 a includesa protrusion, provided at different positions on the projection lens 29,according to whether the f number is 1.85 or 2.2, and the liquid crystalprojector is provided with means of detecting the position of thisprotrusion when a projection lens 29 is mounted; the CPU 6 thusdetermines the f number of the projection lens 29 using this detectionresult.)

At the time of adjustment of the liquid crystal projector at thefactory, the color unevenness and brightness unevenness of a projectedimage when a projection lens with an f number of 1.85 is mounted and thecolor unevenness and brightness unevenness of a projected image when aprojection lens with an f number of 2.2 is mounted, are measured;correction data Cc to compensate for color unevenness and brightnessunevenness when the projection lens with an f number of 1.85 is mounted(according to the incident angular distribution when light to beprojected from the projection lens when the projection lens with an fnumber of 1.85 is mounted is incident on the liquid crystal element 25,and according to the VT curve characteristics of different areas of thepicture plane of the liquid crystal element 25) is stored in theregister 17 (FIG. 6) of the correction data storage unit 16 of thethree-dimensional correction unit 5; and correction data Cc tocompensate for color unevenness and brightness unevenness when theprojection lens with an f number of 2.2 is mounted (according to theincident angular distribution when light to be projected from theprojection lens when the projection lens with an f number of 2.2 ismounted is incident on the liquid crystal element 25, and according tothe VT curve characteristics of different areas of the picture plane ofthe liquid crystal element 25) is stored in the register 18.

When the f number of the projection lens 29 is judged to be 1.85 usingthe f number notification unit 29 a of the mounted projection lens 29,the CPU 6 controls the three-dimensional correction unit 5 to cause thethree-dimensional interpolation processor 15 to refer to the correctiondata Cc in the register 17 among the registers 17 and 18 of thecorrection data storage unit 16, and on the other hand, when the fnumber of the projection lens 29 is judged to be 2.2 using the f numbernotification unit 29 a of the mounted projection lens 29, the CPU 6controls the three-dimensional correction unit 5 to cause thethree-dimensional interpolation processor 15 to refer to the correctiondata Cc in the register 18 among the registers 17 and 18 of thecorrection data storage unit 16.

Otherwise the configuration of the liquid crystal projector is the sameas that of the liquid crystal projector of FIG. 5.

Next, operation of the liquid crystal projector is explained.

When the user mounts the projection lens 29 with an f number of 1.85onto the liquid crystal projector, the CPU 6 uses the f numbernotification unit 29 a to judge that the f number of the mountedprojection lens is 1.85. Then, under control of the CPU 6,three-dimensional interpolation data C(X, Y, Z) obtained based oncorrection data Cc (correction data to compensate for color unevennessand brightness unevenness when a projection lens with an f number of1.85 is mounted) within the register 17 of the correction data storageunit 16 is supplied from the three-dimensional correction unit 5 to thewhite balance adjustment unit 3 and gamma correction unit 4. By thismeans, uniformity correction (white balance adjustment and gammacorrection) are performed on the image signal applied to the liquidcrystal element 25, in the white balance adjustment unit 3 and gammacorrection unit 4 so as to compensate for color unevenness andbrightness unevenness when the projection lens with f number 1.85 ismounted.

On the other hand, when the user mounts the projection lens 29 with an fnumber of 2.2 onto the liquid crystal projector, the CPU 6 uses the fnumber notification unit 29 a to judge that the f number of the mountedprojection lens is 2.2. Then, under control of the CPU 6,three-dimensional interpolation data C(X, Y, Z) obtained based oncorrection data Cc (correction data to compensate for color unevennessand brightness unevenness when a projection lens with an f number of 2.2is mounted) within the register 18 of the correction data storage unit16 is supplied from the three-dimensional correction unit 5 to the whitebalance adjustment unit 3 and gamma correction unit 4. By this means,uniformity correction (white balance adjustment and gamma correction)are performed on the image signal applied to the liquid crystal element25 in the white balance adjustment unit 3 and gamma correction unit 4 soas to compensate for color unevenness and brightness unevenness when theprojection lens with f number 2.2 is mounted.

Thus by performing different correction according to the f number of themounted projection lens even for image signals at the same level and inthe same location of the picture plane of the liquid crystal element 25,appropriate uniformity correction can be performed even when there is achange in the angular distribution of light emitted from the liquidcrystal element 25 and reaching the screen due to the f number of themounted projection lens.

Further, registers 17 and 18 are provided in the correction data storageunit 16 of the three-dimensional correction unit 5 to store two sets ofcorrection data Cc for the characteristics of each area of the pictureplane of the liquid crystal element 25, according to the f number of thereplaceable projection lens. Hence appropriate uniformity correctionaccording to the f number of the mounted projection lens can beperformed more quickly than when using computation to determine thecorrection data Cc according to the zoom position of the currentlymounted projection lens.

Furthermore, the CPU 6 judges the f number of the currently mountedprojection lens, and correction is performed according to the f numberof the currently mounted projection lens based on the judgment result;hence appropriate uniformity correction can be performed automaticallyaccording to the f number of the mounted projection lens.

Next, FIG. 10 shows a modified example of the configuration of theliquid crystal projector of FIG. 9; units common to FIGS. 1, 5, 6, and 9are assigned the same symbols. The projection lens 30 with an f numberof 2.2 shown in the drawing and used as a projection lens to be mountedon this liquid crystal projector is provided with a differential datastorage unit 30 a (as the projection lens with an f number of 1.85, anordinary projection lens not provided with a differential data storageunit 30 a is used).

The differential data storage unit 30 a is configured such that, uponmounting the projection lens 30 on the liquid crystal projector, datawhich is the difference of the correction data Cc stored in register 18(FIG. 6) of the correction data storage unit 16 of the three-dimensionalcorrection unit 5 (correction data to compensate for color unevennessand brightness unevenness when a projection lens with an f number of 2.2is mounted) and the correction data Cc stored in the register 17 (FIG.6) of the correction data storage unit 16 of the three-dimensionalcorrection unit 5 (correction data to compensate for color unevennessand brightness unevenness when a projection lens with an f number of1.85 is mounted) in the example of FIG. 9, is stored in memory (forexample ROM) connected to the CPU 6.

Though not shown, in this example the correction data storage unit 16 ofthe three-dimensional correction unit 5 is provided with only a register(equivalent to the register 17 in FIG. 6) which stores correction dataCc to compensate for color unevenness and brightness unevenness when aprojection lens with an f number of 1.85 is mounted; a register(equivalent to the register 18 in FIG. 6) which stores correction dataCc to compensate for color unevenness and brightness unevenness when aprojection lens with an f number of 2.2 is mounted, is not provided.

When there exists no differential data storage unit 30 a in the mountedprojection lens (when the f number of the mounted projection lens is1.85), the CPU 6 causes the three-dimensional interpolation processor 15to refer to the correction data Cc in the register of the correctiondata storage unit 16, and based on this correction data Cc causes thethree-dimensional correction unit 5 to prepare three-dimensionalinterpolation data C(X, Y, Z).

On the other hand, when there exists a differential data storage unit 30a in the mounted projection lens (when the f number of the mountedprojection lens is 2.2), the differential data is read from thedifferential data storage unit 30 a, and the CPU 6 causes thethree-dimensional interpolation processor 15 to refer to thisdifferential data and the correction data Cc in the register of thecorrection data storage unit 16, and based on the data resulting bysubtraction of this differential data from the correction data Cc,causes the three-dimensional correction unit 5 to preparethree-dimensional interpolation data C(X, Y, Z).

Otherwise the configuration of this liquid crystal projector is the sameas in the example of FIG. 9.

In this example, it is sufficient to store only correction data Cccorresponding to a projection lens of f number serving as a standard (anf number of 1.85) in the correction data storage unit 16 of thethree-dimensional correction unit 5. As a result, in addition toobtaining completely the same advantageous results as in the example ofFIG. 9, appropriate uniformity correction can be performed correspondingto replacement of the projection lens, even when there are numeroustypes of replaceable projection lenses (here there are only two types ofprojection lenses, with f numbers of 1.85 and 2.2, but cases of three ormore types can be accommodated), without causing numerous correctiondata sets to be stored in the correction data storage unit 16 of thethree-dimensional correction unit 5 of the liquid crystal projector mainunit.

In addition to the f number, optical characteristics specific to theprojection lens, such as for example differential data includingcorrection of light amount distribution due to the angle of field of theprojection lens, can also be stored in the differential data storageunit 30 a of the projection lens. Accordingly, the liquid crystalprojector main unit can perform appropriate uniformity correctionaccording to the optical characteristics of individual replaceableprojection lenses.

In the above-described example, a configuration is employed in whichdifferential data is stored in the storage means of a replaceableprojection lens; through the storage means of the projection lens,correction data corresponding to individual projection lenses can bestored, and based on the correction data, various configurations can beemployed in which, the liquid crystal projector main unit can performappropriate uniformity correction according to replacement of theprojection lens.

In each of the above examples, a liquid crystal projector provided witha variable diaphragm, a liquid crystal projector having a projectionlens including a zoom lens, and a liquid crystal projector with areplaceable zoom lens were described separately. However, this inventionmay also be applied to a liquid crystal projector provided with avariable diaphragm and also having a projection lens including a zoomlens, and to a liquid crystal projector provided with a variablediaphragm and with a replaceable zoom lens (with appropriate uniformitycorrection performed according to the combination of the currently openor closed state of the variable diaphragm and the current zoom position,or with appropriate uniformity correction performed according to thecombination of the currently open or closed state of the variablediaphragm and the f number of the currently mounted projection lens).

Further, in the above examples, correction of the image signal appliedto the liquid crystal element 25 is performed according to the twostages, which are the open and closed states, of the variable diaphragm1 (two-stage adjustment of the area of the aperture portion to be largeor small). However, in another example, correction of the image signalapplied to the liquid crystal element 25 may be performed according tothree or more stages of open or closed states of the variable diaphragm1.

In the above examples, this invention is applied to a liquid crystalprojector; however, this invention may be applied to otherprojection-type display devices as well. For example, when providing aDMD® projector with a variable diaphragm, the variable diaphragm may beprovided within the projection lens.

In the example of FIG. 5 above, a variable diaphragm 1 (mechanicalshutter) is used as shielding means. However, in other examples, aliquid crystal shutter composed of a transmissive liquid crystal elementmay be used as shielding means.

Further, this invention is not limited to the above examples, and ofcourse various other configurations may be employed, so long as there isno deviation from the gist of the invention.

As explained above, by means of a first projection-type display deviceof this invention, in an environment with outside light the shieldingamount of the shielding means can be reduced, to make white brighter andpresent a higher-brightness image, whereas in an environment withoutoutside light the shielding amount of the shielding means can beincreased, to suppress white and enhance contrast, with the advantageousresult that a balance between brightness and contrast can be achieved.

Furthermore, while maintaining a balance between brightness andcontrast, there is the advantageous result that appropriate uniformitycorrection can be performed even when there is a change in the angulardistribution of light emitted from the spatial light modulation elementand reaching the screen, due to a change in the amount of shielding ofthe shielding means.

Moreover, there is also the advantageous result that appropriateuniformity correction can be performed even when the output levelcharacteristic of light from the spatial light modulation element withrespect to the image signal applied level is different for differentareas of the spatial light modulation element, and also changes due tothe angular distribution of light incident on the spatial lightmodulation element.

Then, there is a further advantageous result that, according to thesecond projection-type display device of this invention, appropriateuniformity correction can be performed even when there is a change inthe angular distribution of light emitted from the spatial lightmodulation element and reaching the screen due to a change in the zoomposition of the projection lens.

Further, there is the advantageous result that appropriate uniformitycorrection can be performed even when the output level characteristic oflight from the spatial light modulation element with respect to theimage signal application level is different for different areas of thespatial light modulation element, and also changes due to the angulardistribution of light incident on the spatial light modulation element.

There is also the advantageous result that appropriate uniformitycorrection according to the zoom position of the projection lens can beperformed more quickly than when using computation to determine thecorrection data corresponding to the current zoom position of theprojection lens.

Further, there is the advantageous result that appropriate uniformitycorrection according to the zoom position of the projection lens can beperformed automatically.

Furthermore, according to the third projection-type display device ofthis invention, there is the advantageous result that appropriateuniformity correction can be performed even when there is a change inthe angular distribution of light emitted from the spatial lightmodulation element and reaching the screen due to replacement of theprojection lens with a projection lens having a different f number.

Further, there is the advantageous result that appropriate uniformitycorrection can be performed even when the output level characteristic oflight from the spatial light modulation element with respect to theimage signal application level is different for different areas of thespatial light modulation element, and also changes due to changes in theangular distribution of light incident on the spatial light modulationelement.

Further, there is the advantageous result that appropriate uniformitycorrection according to replacement of the projection lens can beperformed more quickly than when using computation to determinecorrection data according to the f number of the currently mountedprojection lens.

Furthermore, there is also the advantageous result that appropriateuniformity correction can be performed automatically according toreplacement of the projection lens.

Moreover, there is also the advantageous result that appropriateuniformity correction can be performed according to replacement of theprojection lens without storing numerous correction data sets in theprojection-type display device main unit, even when there are numerousreplaceable projection lenses.

1. A projection-type display device, comprising: a light source; aspatial light modulation element that modulates incident light accordingto an applied image signal and emits the modulated light; anillumination optical system that condenses light emitted by the lightsource and illuminates the spatial light modulation element with thecondensed light; a projection lens that projects light emitted from thespatial light modulation element; a shielding unit, positioned on eitheran illumination optical system side of the spatial light modulationelement or a projection lens side of the spatial light modulationelement, that varies an amount of shielding of light transmitted throughthe shielding unit to change an angular distribution of light emitted bythe spatial light modulation element; an image signal correction unitthat divides a picture plane of the spatial light modulation elementinto a plurality of areas and performs, for each of the plurality ofareas, uniformity correction on the image signal applied to the spatiallight modulation element in accordance with a current level of shieldingby the shielding unit; and a three-dimensional correction unit thatsupplies, to the image signal correction unit, three-dimensionalinterpolation data C (X, Y, Z) for a level Z image signal at anarbitrary pixel G (X, Y) of the spatial light modulation element, theimage signal correction unit performing the uniformity correction usingthe three-dimensional interpolation data C (X, Y, Z), thethree-dimensional correction unit including: a position computation unitthat determines, based on coordinates (X, Y) of the arbitrary pixel G(X, Y), an address of the arbitrary pixel G (X, Y) and a position blockin which the arbitrary pixel G (X, Y) is located and outputs addressdata (Xb, Yb), and a three-dimensional interpolation unit thatinterpolates output levels for the level Z image signals at arbitrarycoordinates based on the address data (Xb, Yb) received from theposition computation unit and correction data Cc (Xc, Yc, Zc) associatedwith the current level of shielding to generate the three-dimensionalinterpolation data C (X, Y, Z).
 2. A projection-type display deviceaccording to claim 1, further comprising: a horizontal/verticalsynchronization unit that identifies coordinates (X, Y) of the arbitrarypixel G (X, Y), a coordinate data storage unit that stores coordinatedata (Xc, Yc) for a correction center point in the picture plane,correction range coordinate data (X1, X2, Y1, Y2) of a range in thepicture plane over which uniformity correction is to be carried out, andimage signal level correction range data (Z1, Z2), and a position blockidentification unit that receives the coordinates (X, Y) of thearbitrary pixel G (X, Y) from the horizontal/vertical synchronizationunit, receives the coordinate data (Xc, Yc), the correction rangecoordinate data (X1, X2, Y1, Y2), and the image signal level correctionrange data (Z1, Z2) from the coordinate data storage unit, and dividesthe range in the picture plane over which uniformity correction is to becarried out into a plurality of position blocks.
 3. A projection-typedisplay device according to claim 1, further comprising: a correctiondata storage unit having a first register that stores the correctiondata Cc (Xc, Yc, Zc) at the correction center coordinate Gc for a firstlevel of shielding in which an area of an aperture portion of theshielding unit is larger, and a second register that stores thecorrection data Cc (Xc, Yc, Zc) at the correction center coordinate Gcfor a second level of shielding in which the area of the apertureportion of the shielding unit is smaller.
 4. A projection-type displaydevice according to claim 1, further comprising: a correction datastorage unit that stores the correction data Cc (Xc, Yc, Zc) at thecorrection center coordinate Gc for each one of a plurality of levels ofshielding.
 5. A projection-type display device according to claim 1,wherein the image signal correction unit includes a white balanceadjustment unit.
 6. A projection-type display device according to claim1, wherein the image signal correction unit includes a gamma correctionunit.